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. O. E. SGRIBNER. MULTIPLE SWITCH BOARD TESTING APPARATUS.

N0. 330,059. Patented NOV. 10, 1885.

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CHARLES E. SCRIBNER, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE WESTERNELECTRIC COMPANY, OF SAME PLACE.

WlULTlPLE-SWlTCH-BOARD TESTING APPARATUS.

fiPECIFICATIQN formiag part of Letters Patent No. 330,059, datedNovember 10, 1885.

Application filed October 15, 1883. Serial No. 108,985. (No model.)

To all whom it may concern.-

Be it known that l, CHARLES E. SORIBNER,

a citizen of the United States, residing at Ohicago,in the county ofCook and State of Illinois, have invented a certain new and usefulImprovement in Multiple-Switch-Board Testing Apparatus forTelephone-Exchanges, of which the following is a full, clear, concise,and exact description, reference being had to the ac companying drawing,forming a part of this specification.

My invention relates to multipleswitchboard testing apparatus fortelephone exchanges. The connecting-cords at the differ- 1 ent boardsare arranged in pairs and provided with the usual terminal plugs. Thedifferent pairs of plugs at each board preferably rest in contact with acommon connectingpiece. The frames of the different spring-jack switchesare normally insulated from the telephonelines, the frames,however, of aseries of switches belonging to a given line being connected together.At each multiple board I provide a battery in the circuit of theoperators telephone and transmitter. The battery may consist of only oneor two cells.

In the drawing, which is illustrative of my invention I haveshown threemultiple switchboards, 1,2, and 3, and two telephone-lines, a and b,connected each with a switch upon each board and through an annunciatorto ground. The frames of the switches of each line are connectedtogether. Thus the frames of the switches of line a are connected bywire 0, and the frames of the switches of line b are connected by wired, as indicated by dotted .lines in the drawing. The frames of eachseries of switches, though connected together, are normally open toearth. The insertion of a plug in any switch of a series crosses all theswitches of the series with the line which is connected with said plug.

My invention herein is designed to enable an operator to test todetermine whether there is such a cross on a line wanted by means of thesame plug with which he is about to establish a connection with the linewanted.

I have shown so much of the operators apparatus at each of the threeboards as is nec- 5o essary to illustrate my invention. I will describethis testing apparatus in detail as shown at board 3.

The terminal plugs e f of the pair of fleXible connecting-cords rest incontact with the common connecting-pieceg. The clearing-out annunciatorh is included in the circuit of the cords in the usual manner.The'branch circuit z is connected between the two spools of theelectromagnet of the clearing-out annunciator and extends to the key isof the opera- 6o tors telephone Z. The testing-battery m is included inthe circuit with the telephone. The calls of the subscribers are sent inin any well-known way. The operator whose business it is to answer thecalls of a given subscriber, as soon as she sees the callingannunciatorfall, inserts a plug of one of the pairs at her board in the callingsubscribers switch. This is illustrated at board 2, plug it beinginserted in switch 0 of line b. The line b is thus cut off from board 3and connected to ground through the testing-battery m and telephone Z.When the other plug, n, is inserted into switch 0 of another subscriber,the two subscribers will be connected together 7 5 through the pair ofcords, while the telephone Z and battery in will be out of circuit.

The test to determine whether a line called for is in use is made by theoperator while in the act of inserting the plug. The operator at themoment of making the connection with the line of the calling subscribertests to determine whether a connection has been made with the said lineduring the few seconds which may have elapsed since the call was sentin. This test is made at the first contact of plug a with the frame ofswitch 0. If at this first contact of plug it with switch 0 a click isheard in the telephone Z, the operator will know that a plug is insertedin some other 0 switch of the line, forming across,which gives circuitto test battery 11?. through telephone Z. Therefore, when the click isheard, the plug it should not be inserted; but if no click is heard inthe telephone Z the operator at 5 once inserts plug it into switch 0, asshown at board 2. The-same plug is used for testing and for making theconnection with the telephone-line.

The operator having learned which line is called for, must also test todetermine whether the line wanted is in use. In order to determine thisthe opera-tor takes the plug from the switch of the calling subscriberand applies it to the switch of the subscriber who has been called for.Thus, as shown at board I, plug 17 touches the frame of switch q of lineb. The

' line being in use, as shown at board 2,the frame of switch (1 will befound crossed with line b. The operator will discover this by listeningat telephone Z when the battery m 'is closed to line as the plug 19touches the frame ofswitch q. The circuit may be traced from the groundat the central office through telephone Z the transmitter, and battery mto the common connecting-piece, and thence to plugr, and thence throughthe pair of cords to plug p, and thence to the frame of switch q, andthence by line (2 to the frame of switch 0 of the second board, and fromthe point of the plug a to line 12. Thus, if the battery m is closed toline, the operator will hear a click at telephone Z. If she hearsnoclick, she

will insert the plug 19 in switch qand send a call to line b in theusual manner. The other plug, 7', of the pair may then be lifted fromthecommon connecting-piece and inserted inthe switch of the subscriber whosent in the call. The two lines will thus be connected together throughthe pair of flexible cords, and the telephone Z and the test-batterywill be out of the circuit. v

The telephone-key may be usedto connect the telephone with the circuitof the connected lines to enable the operator to listen out.

There are modifications of my invention that will readily suggestthemselves to an electrician which may be made in my apparatus withoutdeparting from myinvention. The operators telephone and battery,forexample,may be included in any part of the circuit between the plugp andthe central-office ground, and any well-known switching apparatus may beused to cut out the said telephone and battery from the circuit of twoconnectedlines. Other forms of switches may also be used upon themultiple switch-boards. I therefore do not limit myself to the specialconstructions shown; but

I claim, broadly 1. In amultiple-switch-board system, atest- I circuitconsisting of a pair of connecting-cords and their terminal plugs,acommon connecting will know that this line, d is open, and the linebnot being in use sheers without including the piece with which the plugsare normally in contact, a ground-connection for said common connectingpiece, and a telephone and testbattery included in said ground-circuit,substantially as and for the purpose specified.

2. The combination, at any one of the multiple switch-boards of atelephone-exhange, of one or more pairs of plugs and cords with a commonconnecting-piece, to which the different pairs of plugs are normallyconnected, and a testing-battery and telephone,whereby when either plugof a pair is applied to the switch of a subscribers line the telephoneand testing-battery will be included in the circuit between said, plugand the central-office ground.

8. The combination, with the switches of a multiple switch-board, of acircuit including a telephone-receiver, a test-battery, and pairs ofcords and plugs normallyin connection with said circuit, whereby a testand connection may be made by means of either one of the plugs of anypair.

4-. The combination,with a pair of connecting plugs andscordsand acommon connectingvpiece-with whichv said plugs are normally in contact,of a branched ground circuit, one branch of saidground-circuit beingconnected through a battery to the common connecting- 7 piece and'theother branch connected through a normally-open listening-key tothecircuit of the connecting-plugs, whereby a connection :may beestablished through the telephone-receiverto the connected lines of twosubscribbattery in circuit, substantially asset forth. V 1

5. The combination, with a pair of connecting plugs and cords, a commonconnectingpiece withwhich said plugs are normally in contact, and aclearing-out annunciator in circuit between the plugs, of a branchedgroundcircuit, one branch of said ground-circuit containing a batteryand being connected to the common connecting-piece, the other branchcontaining a listening-key and being connected between the spools of theclearing-out annunciator, substantially as and for the purpose setforth.

In wi-tnesswhereof I hereunto subscribe, my

name ,t h i s .l-2th day of October, A. D. 1883.

CHARLES. E. SGRIBNER.

Witn .esses GEORGE P. BARTON, PAUL A. STALEY.

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